This invention relates to an ink supplying apparatus for a printing machine, and more particularly to an apparatus for transferring ink from an ink fountain to a printing plate.
A typical apparatus heretofore used for supplying ink to a printing plate in relief printing, offset printing and the like is shown in FIG. 3 of the accompanying drawings. As seen, ink in an ink fountain 1' is taken out by a lifter roller 2' which is adapted to come into and out of contact with an ink fountain roller 1a'. The ink is transferred from the lifter roller 2' to one and then to another of a plurality of distributor rollers 3', 4' which are rotatable in contact with one another. The ink becomes sufficiently distributed in the course of passage through the distributor rollers 3', 4', and is passed to form inking rollers 8' and finally to a printing plate or plate cylinder 9' rotating in contact with the form inking rollers 8'.
The above ink supplying technique permits traces of image portions of the printing plate 9' to remain on the final or form inking rollers 8' as shown in FIG. 4. The form inking rollers 8' are constantly maintained in rotation and in contact with an adjacent distributor roller 4' and after one revolution the rollers 8' are replenished with an amount of ink corresponding to an amount that has been transferred to the printing plate 9'.
However, the cylinder of the printing plate 9' and the form inking rollers 8' are not in a one to one diametric relationship for reasons of design, and an image portion of the printing plate 9' does not turn around to coincide with the same position on the surface of the form inking rollers 8'. Moreover, even though ink is supplemented by the distributor roller 4' as described above, the ink cannot be applied evenly or in an equal thickness to a position on the surface of the form inking rollers 8' corresponding to the image portion and carrying a reduced amount of ink and a position on the surface of the form inking rollers 8' corresponding to a non-image portion carrying an unreduced amount of ink. Therefore, the initial loss of ink to the image portion inevitably remains on the surface of the form inking rollers 8'.
Consequently, when ink is transferred from the form inking rollers 8' after one rotation to a subsequent image portion of the printing plate 9', the ink transfer is carried out while retaining variations in ink thickness corresponding to the preceding image portion as described above. The subsequent image portion transferred from the printing plate to printing paper includes the traces of the preceding image portion, shown as shade portion G in FIG. 5. This greatly deteriorates the quality of finished prints. The shade portions G of printed images thus caused are known as ghosts.